The primary goal of these investigations is to provide a clinical measurement of collagen and elastin matrix degradation in man. Such measurements are currently unavailable, and, in their absence, the diagnosis and the assessment of the clinical course and the response to therapy for a variety of rather common diseases remains uncertain. These diseases include senile osteopenia, Paget's disease of bone, matastatic bone disease, emphysema and chronic obstructive lung disease, and heritable connective tissue disease. Recently we isolated two cross-linking amino acid compounds from human urine, 3-hydroxypyridinium and the desmosines. Both of these compounds represent unambiguous biochemical markers of matrix collagen and elastin. We have demonstrated that levels of urinary desmosine are age- and disease (Marfan's Syndrome)-related (Gunja-Smith and Boucek, 1981, Biochem. J., 193, 815). Harel et al (Amer. Rev. Respir. Dis 122, 769, 1980) have correlated elevated levels with pulmonary disease. Our isolation and characterization of 3-hydroxypyridinium was accomplished by tedious procedures which as such cannot be applied onto the clinical setting. However, we expect to raise antibodies against 3-hydroxypyridinium and to develop a radioimmunoassay, as has been reported for desmosine (Harel et al, abid., King et al, Connect. Tiss. Res. 7, 263, 1980). The availability of specific radioimmune assays for both 3-hydroxypyridinium and the desmosines will be invaluable for assessing the turnover of collagen and elastin matrix and will find broad application in clinical medicine.